Apparatus for conditioning of webs of material



July 22, 1969 o, u so 3,456,361

APPARATUS FOR CONDITIONING OF WEBS OF MATERIAL Filed July 31, 1967 2 Sheets-Sheet 1 Pressure c Suchon chamber Adjacent section Pressure chamber NVENTOR 04 AF 40w GUNbfk'SO/Y BY; 675 z ATTORNEYS APPARATUS FOR CONDITIONING OF WEBS OP MATERIAL Filed July 31, 1967 July 22, 1969 0. A. GUNDERSON 2 Sheets-Sheet u INVENTOR 01. 4/ 41/61/57 'u/voaeso/v %0w7 7 ATTORNEYS United States Patent US. Cl. 34-155 2 Claims ABSTRACT OF THE DISCLOSURE In the treatment of webs of sheets of material with a fluid medium, the medium is uniformly distributed across the width of the material by providing a plurality of separate fluid-applying and -withdrawing sections transversely of the width of the material. In each section, the supply of fresh medium and the exhaust of spent medium are controlled by dampers, and a predeterminable proportion of the medium can thus be recirculated into contact with the material thereby to reduce the net rate of supply and exhaust of the medium. The dividing line between adjacent sections departs from the direction of travel of the material so that no untreated areas remain between sections.

The present invention relates to an improvement in apparatus for conditioning of various materials in the form of webs. The conditioning may include heating, cooling, drying, moistening, thermosetting or other forms of heat treatment, while the materials in question may be webs of textiles, fabrics of synthetic materials, cellulose, paper, felt for paper machines and the like. The conditioning may also include removal of volatile solvents and also application of chemicals to the web if required.

The term webs is in the present case not to be understood as referring only to continuous bands of materials, but can also include sheets of material, for example cardboard to be treated in a suitable manner.

In the course of time there have been many different embodiments of such drying apparatus, and as examples reference can be made to US. Patents Nos. 2,351,549, 2,700,226 and 2,731,732 which disclose drying apparatus for web materials in which hot air is blown through many small nozzles and with high speed onto local areas of the web of material to be dried, the drying medium being immediately withdrawn by suction through openings located close to the nozzles for the hot air.

The temperature of the web may be controlled by regulating the temperature of the air, by adjusting the speed of the air flow or by other methods. One is, however, confronted with a substantial problem with regard to achieving an even distribution of the supply or removal of heat from the web of material or of other media to be transferred to or removad from the web, and this problem is more complicated the greater the width of the web. As an example, paper machines in use at the present time may have a web width of 8 to 10 meters, which means that, during production, the web of the paper machine prior to the drying process may have a width of 12 meters.

The medium to be supplied to the web and withdrawn from same through respective nozzles and openings, is conveyed to the nozzles through long channels which extend across the whole width of the web of material, and when said channels are of the length mentioned above, the pressure drop in the channels, from one end to the other, results in an uneven distribution of heat to the web, and thereby uneven temperature, which then causes for example an uneven thermosetting or drying.

Supply of heat by blowing of the drying medium for 3,456,361 Patented July 22, 1969 ice instance in the form of hot air, and immediate withdrawal thereof by suction also entails an uneconomical utilization of the heat contained in the air, since, without having released a great amount of heat, it is returned, through pipes and conduits, to the location wherein the hot air is reheated for re-circulation through the drying apparatus.

The object of the present invention is primarily to overcome the above mentioned disadvantages so as to achieve, in a far more satisfactory manner than has previously been possible, an even conditioning, for example by controlling the temperature over the whole Width of the web of material. When utilizing the invention, moreover, it is possible to use a much smaller size of channel for supply of the conditioning medium and for the withdrawal thereof by suction, since the active properties of the medium can be utilized to a much greater extent.

This is in accordance with the invention, achieved by dividing the apparatus which extends over the whole width of the web, into sections, for instance ten sections over a width of 12 meters. Each section is connected to channels or conduits for supply and withdrawal of conditioning medium (for example hot air for drying or heating) and, in addition, each section contains a blower with channels and chambers in connection with the blower in such a way that the medium blown onto the web of material through suitable nozzles and withdrawn immediately from the web through openings, is circulated through the section and returned to the nozzles to increase the utilization of the active properties of the conditioning medium used to treat the web of material. The treatment may, as mentioned above, consist in supply or removal of heat, moistening etc. By means of this re-circulation of the treatment medium, a certain quantity of unused medium may be supplied to the sections from the supply channel which extends along and is connected to all of the sections of the drying apparatus and at the same time, a corresponding quantity of used medium may be withdrawn through the suction channel, which in the same way is connected to all the sections of the apparatus. The supply of treatment medium and withdrawal thereof takes place through suitable openings provided with valves, and by adjustment of these valves it is possible at all times to control for example the heat quantity or quantity of moisture supplied and thereby also the treatment of that width of web of material upon which one section acts. In this way one achieves, amongst other things, an improved distribution of active components or properties and a more expedient utilization of same in the medium, without the necesstiy of conveying the medium in long channels prior to its being recycled to the web of material.

A blower in each section ensures constant blowing velocity for the treatment medium at all times and in all locations. The temperature or other properties of the medium are regulated or held constant by varying the supply of unused medium by means of the two valves described hereinbefore. Constant speed and properties of the treatment medium are thus achieved, but it is possible to control or adjust both as desired. The result is a uniform and stable conditioning of the web of material, and the blowing velocity is reduced by decreasing heat requirement.

Inasmuch as each section affects a fraction of the width of the web to be treated, corresponding to the width of the section, it is possible that when a travelling web is to be treated, the area of the web of material passing over the dividing line between adjacent sections will receive a reduced quantity of the treatment medium. In accordance with the invention, however, this disadvantage is overcome in that at least the surface over which the web passes, where are located the nozzles and openings for supply and withdrawal of the treatment medium, is divided into sections along lines which depart from the direction of travel of the web. In this manner the entire width of the web of material will be covered by nozzles and openings for the treatment medium.

The invention thus concerns an improvement in an apparatus for conditioning webs of materials, for example textiles, fabrics, cellulose, paper, felts for paper machines, and also sheet material, for example cardboards and the like, and the apparatus is of the type in which a conditioning or treatment medium which is to be blown onto the web of material and withdrawn therefrom by suction, is supplied and withdrawn through channels and conduits extending over the entire width of the web transversely of its direction of travel, the supply and withdrawal of the medium being carried out through suitable nozzles and openings respectively which are in communication with said channels and are directed to the web of material on one or both sides thereof, and the invention is mainly characterized in that the apparatus is divided into sections extending in juxtaposed position transversely of the longitudinal direction of the web and is connected to said channels, and provided with equipment for circulation of some or all of the withdrawn conditioning medium prior to said medium being conveyed into the suction channel.

A further and important feature according to the invention, is that the direction of the dividing line between adjacent sections departs from the direction of travel of the web.

Further, in accordance wtih the invention, it is an advantage that the equipment for recirculation of the treatment medium comprises a blower separately driven, and adjustable valves for regulating the quantity of treatment medium to be recirculated or renewed, and it is also a distinguishing feature of the invention that each section is constructed around a blower, the pressure side of which is connected to at least one pressure chamber which is connected to blowing nozzles, the suction side of said blower being connected to the suction openings and having two valves leading to respective channels for supply and withdrawal of the treatment or conditioning medium.

Further features and details of the invention will be evident from the following description with reference to the drawings on which:

FIG. 1 very simply and purely diagrammatically shows a section seen in perspective with some of the walls removed to disclose the interior of the section, and

FIG. 2 shows, also diagrammatically, a top view of parts of adjoining sections.

In the following description it is presumed that the web of material is to be dried and that the drying medium is hot air, but it is to be understood that any treatment involving the use of treatment mediums which can be conveyed through channels and conduits, can be used effectively on all types of webs and sheet materials.

The main channel for supply of hot air and for withdrawn air extends the whole width of the web of material. On the drawing, however, only the portion located beneath a section of the drying apparatus is shown. The control valve, which may be coupled to and controlled by temperature sensors at the web of material, leads from the main channel into a suction chamber connected to the suction side of a circulation blower which circulates air about a path within the associated section. The pressure side of said blower opens into the pressure chamber which is located on both sides of the sections in the embodiment shown. Nozzles are in communication with the pressure chambers for blowing the hot air onto the web and, in the shown example, they are in the form of channels having narrow slots directing the air onto the web of material to be dried. Between these channels are located suction openings formed between the nozzles for the hot air. The withdrawal openings may be limited by a plate provided with holes disposed over the nozzle channels. This is indicated at one end of the shown section, and the nozzles for hot air and the withdrawal openings for the same air are evenly distributed on the top side of the section, e.g. over a length of two meters and a w1dth of 1.2 meters.

The control valves in the main channel are both on the suction side of the blower and are coupled together so that they open respectively to the same extent. When the drying apparatus is started, hot air is pressed through the valve from upstream of the valve in one main channel to the circulation blower and therefrom into the pressure chambers which convey the hot air into the nozzles. At the same time the suction chamber is connected to the withdrawal openings between the nozzles for hot air, and the hot air which is blown onto the web is then immediately withdrawn by suction into the suction chamber. Subsequent to the drying apparatus being filled with hot air in this manner, it may be necessary for one reason or another, e.g. too high temperature, to re-circulate all the air which is withdrawn from the web of material through the withdrawal openings. The control valve is then closed and the section operates as an independent unit. When the temperature falls below the value desired for the drying, further heat energy must be supplied by further supply of hot air. This is accomplished by opening the control valves in the main channels for hot air. The control system is preferably constructed so that the valves, during normal operation, operate constantly in intermediate positions, i.e. neither entirely open nor entirely closed.

In other words, hot air from main channel 6 passes through control valve or damper 7 into suction chamber 8 and thence into the suction side of blower 9. The hot air emerges from the pressure side of blower 9 and is divided and passes into pressure chambers 10 on either side of suction chamber 8. Pressure chambers 10 open upwardly only through conduits in the form of channels 11, which of course do not communicate at all with suction chamber 8. Indeed, channels 11 open upwardly through narrow slots 12, which in turn are directed upwardly through the holes 13 in plate 14 over which the material travels.

The hot air, after having thus contacted the material, passes back down through holes 13 to the spaces between channels 11, which spaces communicate with suction chamber 8. Part of the returning air is recirculated to the suction side of blower 9; while the rest passes through control valve or damper 15 to exhaust channel 16 from which it is discharged.

As previously stated, it has proved to be expedient, inter alia in the production of felts for paper machines, to divide the drying apparatus into ten sections when the web width is 12 meters. Thus, each section affords heat treatment to a tenth part of the width of the web, and, with the means hereinbefore described, it is evident that each section is capable of effecting the same heat treatment of the web passing the section, regardless of where the section is located in the width.

However, there will be, between two adjacent sections, narrow portions which have no equipment for heat treatment or drying of the web of material, and, in some cases, this leads to the formation of untreated stripes or bands in the web of material. This problem is solved, however, by dividing the operational surface of the sections along lines extending at an angle to the centre line of the apparatus shown in FIG. 2, where 1 signifies the surface of a section, and 2 and 3 are parts of adjacent sections. The direction of travel of the web of material relative to the sections 1, 2 and 3, is shown by the arrow 4, and it is easily seen that the dividing lines 5 between the sections 1 and 2 and 1 and 3, extend obliquely relative to the direction of travel, whereby the parts of the web of material which arrive above the heat treatment apparatus at a partition line where no heat treatment occurs, will not follow this line, but traverse other parts of the section.

In addition to the above described advantages, an apparatus for conditioning the web of material, constructed in accordance with the invention, also offers the extremely important advantage that the apparatus in a very simple manner can be adapted to the conditioning or treatment of webs of varying widths. If both control valves are closed in a section and the circulation blower is stopped, the section will be out of operation, and for a narrower width than the maximum for which the apparatus is constructed, it is possible to select the sections desired to be in operation, these being selected from either side of the apparatus or disposed centrally in order to distribute the wear and tear on the treatment sections during the course of time. The extremely accurate control of the conditioning of the whole width of the web is particularly important for thermosetting of certain artificial materials which requires great accuracy.

The example shown serves merely to illustrate the invention and forms no restriction to the protection afforded by this patent, since other embodiments are possible within the scope of the invention, isofar as the apparatus is divided into sections with the possibility of recirculation of some or all of the conditioning medium supplied to the section, so that the medium may be repeatedly brought into contact with the web of material without having first passed through long main channels.

Having described my invention, I claim:

1. In apparatus for treating webs, in which hot air is blown onto the web and withdrawn therefrom by suction, through channels extending transversely of the direction of travel of the 'web, the blowing and withdrawal being carried out through nozzles and openings which are in communication with said channels and are adapted to direct the conditioned air onto the web on at least one side of the web, and in which the apparatus is divided into juxtaposed sections transversely of the longitudinal direction of the web with a blower in each section for recirculating air about a path; the improvement comprising a pair of adjustable valves in each section for controlling the amount of air recirculated through the blower, one of said adjustable valves in each section communicating between said path and a supply channel for conditioned air and the other of said valves in each section communicating between said path and an exhaust channel for withdrawing spent air from the section, and means for supplying hot air to said supply channel upstream from said one valve, said valves in each section being both disposed on the same side of said blower.

2. In apparatus for treating webs, in which hot air is blown onto the web and withdrawn therefrom by suction, through channels extending transversely of the direction of travel of the web, the blowing and withdrawal being carried out through nozzles and openings which are in communication with said channels and are adapted to direct the conditioned air onto the web on at least one side of the web, and in which the apparatus is divided into juxtaposed sections transversely of the longitudinal direction of the web with a blower in each section for recirculating air about a path; the improvement comprising a pair of adjustable valves in each section for controlling the amount of air recirculated through the blower, one of said adjustable valves in each section communicating between said path and a supply channel for conditioned air and the other of said valves in each section communicating between said path and an exhaust channel for withdrawing spent air from the section, and means for supplying hot air to said supply channel upstream from said one valve, the direction of the dividing line between adjacent sections departing from the direction of travel of the web.

References Cited UNITED STATES PATENTS 2,919,495 l/1960 Underhay et al 341 14 3,052,991 9/1962 Goldner 34-4 XR 3,089,252 5/1963 Daane et al. 34-160 XR 3,203,678 8/ 1965 Sawyer et a1. 3,214,845 11/1965 Huffman. 3,284,920 ll/1966 Hayrinen et al. 34-155 XR CARLTON R. CROYLE, Primary Examiner ALLAN D. HERRMANN, Assistant Examiner 

